Objective-To examine whether reactive arthritis (ReA) known to occur after a urogenital infection with Chlamydia trachomatis can also follow an infection with Chlamydia pneumoniae, a recently described species of Chlamydiae that is a common cause of respiratory tract infections. Methods-Specific antibodies (microimmunofluorescence test) and lymphocyte proliferation to C trachomatis and C pneumoniae in paired samples of peripheral blood and synovial fluid were investigated in 70 patients with either reactive arthritis (ReA) or undifferentiated oligoarthritis (UOA). Results-Five patients with acute ReA after an infection with C pneumoniae are reported. Three had a symptomatic preceding upper respiratory tract infection and two had no such symptoms.In all patients a C pneumoniae-specific lymphocyte proliferation in synovial fluid and a high specific antibody titre suggesting an acute infection was found. Conclusion-C pneumoniae needs to be considered a new important cause of reactive arthritis.

Objective. To investigate the effect of long-term antibiotic treatment in patients with reactive arthritis (ReA) and undifferentiated oligoarthritis. Methods. One hundred twenty-six patients were treated with ciprofloxacin (500 mg twice a day) or placebo for 3 months, in a double-blind, randomized study. Of these patients, 104 (48 treated with cipro-floxacin and 56 treated with placebo) were valid for clinical evaluation: 55 were diagnosed as having ReA with a preceding symptomatic urogenic or enteric infection and 49 as having undifferentiated oligoarthritis. These 2 groups were randomized separately. The triggering bacterium was sought by serology and/or culture. The percentage of patients in remission after 3 months of treatment was chosen as the primary efficacy parameter. Results. A triggering bacterium could be identified in 52 patients (50%): Chlamydia trachomatis in 13, Yersinia in 14, and Salmonella in 25. No patient was positive for Campylobacter jejuni or for Shigella. No difference in outcome was found between treatment with ciprofloxacin or placebo in the whole group or in subgroups of patients with ReA or undifferentiated oligoarthritis. No difference was seen in patients with a disease duration <3 months. Ciprofloxacin was not effective in Yersinia-or Salmonella-induced arthritis but seemed to be better than placebo in Chlamydia-induced arthritis. This difference was not significant, however, which might be due to the small sample size. Conclusion. Long-term treatment of ReA with ciprofloxacin is not effective; however, it might be useful in the subgroup of patients who have Chlamydia-induced arthritis. This has to be proven in a bigger study focusing on patients with Chlamydia-induced arthritis.

Conclusions-Chlamydiatrachomatis, yersinia, and salmonella can be identified as the causative pathogen in about 50% of patients with probable or possible ReA if the appropriate tests are used. (Ann Rheum Dis 2001;60:337-343) Reactive arthritis (ReA) is a well known complication of enteric infections caused by yersinia, salmonella, shigella, and campylobacter, or of urogenital tract infections caused by Chlamydia trachomatis.

Reactive arthritis (ReA) occurs after a urogenital infection usually with Chlamydia trachomatis or an enteritis due to Yersinia, Salmonella, Campylobacter or Shigella, Shigella, except during epidemics, is not considered to be a frequent cause of enteric reactive arthritis. However this might be due to the lack of a reliable antibody test, which makes diagnosis difficult. We compared synovial and peripheral blood lymphocyte proliferation to various bacterial antigens in 19 consecutive patients with ReA or undifferentiated oligoarthritis. In five patients Shigella was identified as the causative microbe by a specific synovial lymphocyte proliferation. All five patients had a history of symptomatic diarrhoea and had negative stool cultures by the time arthritis developed. Four of the five were HLA B27 positive. We conclude that Shigella may be underestimated as a cause of non-epidemic ReA.

The cellular immune response seems to be important for the pathogenesis of reactive arthritis (ReA) and a bacteria-specific lymphocyte proliferation (LP) is often found in synovial fluid (SF) of ReA patients. However, the role of the bacteria-specific LP in peripheral blood (PB) is less well defined. In this study, we investigated 215 paired samples of SF and PB from patients with ReA (n = 65), undifferentiated oligoarthritis (n = 133) and undifferentiated spondylarthropathy (n = 17) to analyse the LP in PB and SF in relation to time. In 24 out of 87 patients (27.6%) with a bacteria-specific LP in synovial fluid, a positive LP to the same bacterium was also found in PB. While a positive LP in SF was found most frequently in the first week of the arthritis, a positive LP in PB was detected in 45% of patients when investigated between weeks 2 and 4 after the onset of arthritis, but was rarely found very early and late in the course of the arthritis. The time point seems to be crucial for the investigation of an LP in PB in patients with ReA.